1. Movement of water in plants
Starter: Which of these leaves are adapted to hot and dry? Which ones are adapted to damp and dark? How? a b c d

2. Adaptations of leaves
Hot and dry Damp and dark b a c d

3. Water movement through plants
How does water move through a plant?
Which part of the plant does water enter?
Which part of the plant does water leave?
What do you know already?
With the person next to you discuss for 1 minute what you already know about the movement of water through plants

4. Roots Functions: Anchorage Storage Transport Absorption
Roots absorb large amounts of water and dissolved minerals from the soil.

5. Root hair cells
Are found near the tips of roots that are growing through the soil.

6. Notes  This gives the cell a much larger surface area than usual.
Each root hair cell has a long thin part reaching out into the soil.
Notes
 This gives the cell a much larger surface area than usual.
 The large surface area means that a lot of water and inorganic ions can get into the cell quickly.
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(4)
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7. Transpiration in plants

9. Need for transport systems
Plants need sugars and water to stay alive
Sugars need to travel from the leaves to the rest of the plant
Water needs to travel from the roots to the leaves

10. Xylem Hollow dead cell tubes
Water and minerals transported in an upwards direction
Very strong so help support the plant

11. Let´s have a look at some celery xylem under the microscope!
Draw what you see!

12. Phloem Transports sugar around plant Made of living cells
Companion cells provide the energy for the tube cells.
The end walls of the tube cells have pores through which food is transported from cell to cell in the form of dissolved sugars (by diffusion)

13. Root Hair Cells soil to xylem root hairs have high surface area to aid
water and mineral absorption
water enters the root hair by osmosis
water enters the xylem by osmosis
minerals enter the root hair by diffusion

15. Water Movement
Mass flow of water in xylem vessels – pressure lowered as water leaves vessels. Water moves up from the roots where the pressure is higher.
Diffusion of water through cells from xylem.
Water vapour diffuses through leaf air spaces.
If the concentration of water vapour in the leaf is higher than outside, water vapour will diffuse out of the leaf through the stomata.
Capillary action (water molecules attracted to polar molecules in xylem walls (adhesion)).
Cohesion – tension theory.

16. Cohesion-Tension Theory
Water molecules have dipoles which cause an attraction between them.
Water is ‘pulled’ up the xylem vessels by transpiration. When this happens, the pull is transmitted all the way down the water column, pulling all of the water molecules up the vessel.
For this to work, the xylem vessel must be a continuous column of water i.e. contain no bubbles.

19. Opening/ Closing Stomata
Stomata can be closed to prevent water loss.
Guard cells curve apart when turgid.
When flaccid, the edges of the cells lie close together.
However, this drastically slows transpiration and means that no carbon dioxide can enter the leaf (= no photosynthesis).

20. Stomata Diagrams

22. xylem to air
transpiration creates a water concentration gradient in the leaves
water moves from the xylem to the surrounding leaf cells by osmosis – where it is used in photosynthesis
water travels through the leaf cells by osmosis
water evaporates from the leaf cells into air spaces and out through the stomata by diffusion
water also travels across the leaf by diffusion via the permeable cell walls and intercellular spaces

23. define transpiration stream
the evaporation of water from the leaves of plants
define transpiration stream
the unbroken path taken by water through a plant from the roots to the leaves
Review osmosis
Hot summer – shrinkage in tree girth
Drinking straw analogy
Capillary action

24. Factors Affecting Water Loss
Diffusion rate is affected by:
Surface area (the higher the surface area, the greater the rate of diffusion).
Difference in concentration (the greater the concentration gradient, the higher the rate of diffusion).
Length of the diffusion path (the greater the length, the lower the rate of diffusion).

25. Preventing Excess Water Loss
Cuticle (waxy layer) on leaf which is impermeable to water.
Most stomata found on underside of leaf as it is cooler in dicotyledons.
Thick leaves = reduced water loss.
Spines/ hairs increasing boundary layer (undisturbed layer of air).
Stomata closed at certain times of the day.
Stomata may be sunken and found in pits.

26. discuss the cooling effect of transpiration
transpiration can lower the leaf temperature by 10-15°C
this prevents the inhibition of enzymes
state the factors affecting the rate of transpiration
increasing temperature increases the transpiration rate
increasing humidity decreases the transpiration rate
increasing wind speed increases the transpiration rate
other factors that control the opening and closing of the stomata include light intensity, availability of soil water and air pollution

27. describe how to measure the transpiration rate
a weight or bubble potometer is used to measure the transpiration rate (Note: it really measures uptake of water by the plant – some of that water will be used in photosynthesis and some will leave the plant by transpiration.)

29. Affecting the rate of transpiration
Light intensity decreases
Temperature increases
Air movement increases
Humidity decreases
CAN YOU WORK OUT WHY THESE THINGS INCREASE THE RATE OF TRANSPIRATION AS A GROUP?

30. What did you learn today?
1. What is the scientific name for water moving through a plant? Transpiration 2. What is the name of the vein in plants that water moves through? Xylem 3. Give 4 ways in which water is useful in plants Cools it down when it evaporates, used for photosynthesis, support, carries dissolved minerals

31. What did you learn today?
4. How do plants use osmosis to help them regulate water loss? Water osmoses into or out of the guard cells to open or close stomata. If guard cells are turgid, stomata is open. 5. Give 4 ways in which plants reduce water loss from them Few stomata, small leaves, stomata on the bottom of leaf, ability to close stomata (waxy cuticle)

32. What did you learn today?
6. Why do water particles move out of the air spaces in leaves into the air? Because there is a higher concentration of water particles in the air space than outside the leaf so the water particles diffuse out of the leaf